The Gulfstream jet was recently spotted on the tarmac at an airport in Sydney, where he visited the official residence of the Australian Prime Minister after flying in from a vacation on Lizard Island in Queensland's Great Barrier Reef. The jet burns 1700 liters of fuel each hour as he zips around the world strumming up business for his firm, Breakthrough Energy, whose stated aim is driving innovation and sustainable energy and technology in order to decrease greenhouse gas emissions.

Gates, who is currently the fourth-richest person in the world, addressed guests at the Lowy Institute think tank in Sydney, emphasizing the importance of reducing greenhouse gases and saying: "The reason why climate change is worth investing in massively is because it will get worse and worse over time. If you allow the warming to go to an extreme level, then all sorts of natural ecosystems disappear and all sorts of places in the world you can't do outdoor work. So the tropical areas, agriculture would be impossible, outdoor work during large parts of the year would be impossible."

Gates wants the world to reduce emissions but has a $194 million private jet collection